In the generic device known from EP 0 625 228 B, corresponding to U.S. Pat. No. 5,490,538, the support member formed as a pipe clamp interrupted in the circumferential direction at the same time serves as a connection-establishing retaining means of the device at the downpipe. The branch pipe is inserted into the opening in the downpipe with the catching blade ahead. The support member formed as a pipe clamp is clamped onto the periphery of the downpipe to position the device on the downpipe. The support member is formed with a noncircular cross-section so that projections formed at the plug-in pipe provide an anti-rotation device. For additionally positioning and sealing purposes, a pipe socket is formed on the support member, into which said pipe socket the branch pipe is inserted. The assembly of the device at the downpipe is complex. The retaining effect of the open pipe clamp is unsatisfactory. The device substantially only fits for a determined downpipe dimension.
A device known from GB 2 248 262 A is fixed directly within the assembly and branching opening of the downpipe by positive insertion without the aid of a support member until the water-catching blade abuts at the contact position disposed at the interior wall of the downpipe and snap tabs disposed at the root of the water-catching blade engage behind the edge of the assembly and branching opening.